Objects for the Microscope. 99 



Gasterophilus, or Stomach-lover. A tawny body very hairy, 

 wings dingy white, and with a transverse gray band ; with- 

 out any proboscis, for it lives but a very short time only 

 to lay its eggs and die. The abdomen is bent inwards, the 

 female having a retractile tube consisting of four pieces, 

 and terminating in five points, within which she holds the 

 egg, and hovers over the horse, lightly darting at him, 

 and depositing each egg upon a hair. This egg is firmly 

 attached by some glutinous substance, and is, as you may 

 observe, finely striated and furnished with an operculum or 

 lid, hinged and fitted on that oblique top. When the larva 

 is fully formed, the egg, which is always placed where the 

 horse most frequently licks itself, opens under the warm 

 moisture of the tongue, and the larva, which is provided 

 with hooks for the purpose, clings to the tongue, and is 

 swallowed with the saliva or the food. By two long sharp 

 hooks you may see folded downwards on the larva it attaches 

 itself to the inner coat of the horse's stomach, nourished 

 by the warmth and the mucus until the spring, when it has 

 grown nearly an inch long ; it then unhooks itself, mingles 

 with the food, and passes out as what grooms call bots. 

 The next change is that it wriggles into the earth, and 

 becomes a pupa, lies there a few weeks, and comes forth as 

 a perfect fly, to rise up and seek its mate, who dies imme- 

 diately after their union, and the female lingers but a few 

 days longer, to deposit a hundred eggs, or more, as her 

 appointed task on earth. 



